The Ethiopian Hydrophane Opals are formed through a process that involves the interaction of water and silica-rich volcanic rocks. The process begins with the deposition of the silica from hot water or steam that seeps into the voids or cracks of the volcanic rock. Over time, the silica forms into tiny spheres that are tightly packed together, creating a lattice structure that diffracts light and produces the iridescent colors that opals are known for.